live555 獲取每一幀

testRTSPClient 中

Boolean DummySink::continuePlaying() {
  if (fSource == NULL) return False; // sanity check (should not happen)

  // Request the next frame of data from our input source.  "afterGettingFrame()" will get called later, when it arrives:
  fSource->getNextFrame(fReceiveBuffer,
 
 DUMMY_SINK_RECEIVE_BUFFER_SIZE,
                        afterGettingFrame, this,
                        onSourceClosure, this);

  return True;
}

獲取了fReceiveBuffer ，完整的一幀資料,可以選擇在afterGettingFrame()中處理

在解碼的過程中我使用了ffmpeg

將接收的每一幀儲存成 h264 裸流檔案（可用vlc 檔案播放）

//開啟檔案 file.h264
File *fp_h264 = fopen("file.h264"
 
,"ab+")//append 形式開啟檔案流

//初始化 引數  使用H264解碼
av_register_all();
AVCodec *m_pAVCodec = avcodec_find_decoder(AV_CODEC_ID_H264);
AVCodecContext  *m_pAVFrame = av_frame_alloc();
AVFrame  *m_pAVCodecContext = avcodec_alloc_context3(m_pAVCodec);

下面就是處理NALU 的轉化為h264,通過0x00 00 00 01 區分NALU ，在testRTSPClient 的afterGettingFrame 中處理

  //定義一個結構體來儲存一幀
  typedef struct {
	  unsigned char * frameBuf;
	  int framebufsize;
  }FrameUnit;
  FrameUnit *pFrameunit = NULL; 
  
  if (!strcmp(fSubsession.mediumName(), "video"))//只處理視訊流
  {
     //給結構提分配記憶體
     pFrameunit = (FrameUnit*)malloc(sizeof(pFrameunit));
     
     char *pbuf = (char *)fReceiveBuffer;
     //每一幀之間的startcode 
     char head[4] = { 0x00, 0x00, 0x00, 0x01 };
     //在每一幀之間加上start code 
     //,0x0000001+sps+0x00000001+pps+0x00000001+NALU1+0x00000001+NALU2
     pFrameunit->framebufsize = frameSize + 4;
     pFrameunit->frameBuf = (unsigned char *)malloc(pFrameunit->framebufsize);
     memcpy(pFrameunit->frameBuf, head, 4);
     memcpy(pFrameunit->frameBuf + 4, pbuf, frameSize);
     //儲存檔案
     fwrite(pFrameunit->frameBuf, pFrameunit->framebufsize, 1, fp_h264);
     //釋放記憶體
     free(pFrameunit->frameBuf);
     pFrameunit->frameBuf = NULL;
     pFrameunit->framebufsize = 0; 
     //當全部寫完fclose
     fclose(fp_h264);
  }

以上就是完整的步驟，用vlc 播放file.h264 就可以

值得學習的是通過ffmpeg 解碼轉為YUV格式

同樣的流程，不過在處理每一幀的資料時候，為ffmpeg的AVCodecContext新增extradata ，即 sps和pps
在處理每一幀資料之前將sps pps 解析出來並且新增到AVCodecContext中

//開啟檔案file.yuv
File *fp_yuv fopen("file.yuv"ab+")
//處理解碼需要的sps 和pps
if (!strcmp(fSubsession.mediumName(), "video"))
  {
      //判斷AVCodecContext->extradata 是否有資料
	  if (m_pAVCodecContext->extradata == NULL)
	  {
		  unsigned int SPropRecords = -1;
		  SPropRecord *p_record = parseSPropParameterSets(fSubsession.fmtp_spropparametersets(), SPropRecords);
         //sps pps 以陣列的形式儲存SPropRecord中
		  SPropRecord &sps = p_record[0];
		  SPropRecord &pps = p_record[1];
		  int totalsize = 0;
		  unsigned char* tmp = NULL;
		  unsigned char nalu_header[4] = { 0, 0, 0, 1 };

		  totalsize = 8 + sps.sPropLength + pps.sPropLength;
          //在每個sps 和pps 之前加上startcode 
		  tmp = (unsigned char*)realloc(tmp, totalsize);
		  memcpy(tmp, nalu_header, 4);
		  memcpy(tmp + 4, sps.sPropBytes, sps.sPropLength);
		  memcpy(tmp + 4 + sps.sPropLength, nalu_header, 4);
		  memcpy(tmp + 4 + sps.sPropLength + 4, pps.sPropBytes, pps.sPropLength);
          //將 sps 和pps 的資料給ffmpeg的h264解碼器上下文
		  m_pAVCodecContext->extradata_size = totalsize;
		  m_pAVCodecContext->extradata = tmp;
	  }
	  //下面的步驟和儲存h264一樣，只是在儲存檔案的地方修改成解碼
	  
      if (fp_yuv) {
      		AVPacket *avpkt = (AVPacket *)malloc(sizeof(AVPacket));
			AVFrame *pFrameYUV = av_frame_alloc();
			AVFrame *pFrameVideo = av_frame_alloc();
			int got_picture = 0;
			av_init_packet(avpkt);

		    //將每一幀賦值給AVPacket
			avpkt->data = frameunit->frameBuf;
			avpkt->size = frameunit->framebufsize;
			if (avpkt->size > 0)
			{
				//解碼一幀，成功返回got_picture 1 ，解碼資料在pFrameVideo
				int ret = avcodec_decode_video2(m_pAVCodecContext, pFrameVideo, &got_picture, avpkt);
				if (ret < 0) {
					env << "Decode :Error.\n";
					goto error_handler;
				}
			}
	        //解碼成功，轉化為 yuv 
			if (got_picture)
			{
			   //下面的步驟，將pFrameVideo轉為pFrameYUV
				uint8_t * out_buffer = (uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, m_pAVCodecContext->width, m_pAVCodecContext->height));
				avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, m_pAVCodecContext->width, m_pAVCodecContext->height);
				struct SwsContext *img_convert_ctx = sws_getContext(m_pAVCodecContext->width, m_pAVCodecContext->height
					, m_pAVCodecContext->pix_fmt, m_pAVCodecContext->width, m_pAVCodecContext->height
					, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
				sws_scale(img_convert_ctx, (const unsigned char* const*)pFrameVideo->data, pFrameVideo->linesize, 0
					, m_pAVCodecContext->height, pFrameYUV->data, pFrameYUV->linesize);
			//輸出出YUV資料  儲存在file.yuv
               int y_size = m_pAVCodecContext->width * m_pAVCodecContext->height;
 				if (mFrameYUV->data[0])	
					fwrite(mFrameYUV->data[0], 1, y_size, fp_yuv);       //Y   
 				
 				if(mFrameYUV->data[1])
 					fwrite(mFrameYUV->data[1], 1, y_size / 4, fp_yuv);   //U  
				if(mFrameYUV->data[2])
					fwrite(mFrameYUV->data[2], 1, y_size / 4, fp_yuv);   //V  
				return 0;
			}
            //釋放
			av_frame_free(&pFrameYUV);
			av_frame_free（&pFrameVideo);
			av_free_packet(avpkt);
			fclose(fp_yuv);
		}
		....
  }

選擇yuv 播放器，選擇720P格式播放

最後就是尋找一個類似SDL 來播放